After returning from Los Angeles, Rebecca marvels at how important a stranger can become. Jack meets Miguel, a store clerk who lends him a sports coat for meeting Rebecca's parents. Rebecca's father tells Jack that he isn't good enough for Rebecca. Three new characters are introduced. Marine NCO Cassidy Sharp returns home, experiencing alcoholism and PTSD. Her husband kicks her out after she strikes their son. A drunk Nicky vandalizes the VA during Cassidy's support group, and contacts Kevin for bail money.

Jack and Rebecca take the young Big Three to the pool at summer's end. Kevin hurts Randall by mocking him in front of his friends, leading Kevin to question if he is a good person; Jack reassures him that only a good person would care. Two popular girls convince Kate a popular boy will kiss her. When instead Stuart—an unpopular boy who actually likes Kate—arrives, she kisses him.

Starting junior high, Randall suffers his first panic attack upon receiving a dress code violation. Kevin forges Rebecca's signature on the slip, and convinces the family to watch Arsenio Hall together to remedy Randall's pop culture deficit. Jack makes a mistake at work; Miguel saves Jack’s job by threatening to quit; Jack pledges to support Miguel whenever needed. In the present, Nicky suffers a setback when his VA therapist is transferred, leading to his vandalism; Nicky may avoid jail time by continuing therapy. Kevin bonds with Cassidy's son Matty in the waiting room. When Kevin takes Nicky to an AA meeting, Cassidy is there; she, Nicky, then Kevin laugh at Kevin's egocentrism. Kate is stunned but ultimately supportive of Toby's fitness.

After Randall and Beth's first date, Rebecca and Carol visit campus and discuss widowhood. Carol believes Randall is too "broken" in grief to support Beth. But, recognizing Randall pays meaningful attention to her, Beth kisses him. A flirtatious record store employee named Marc hires eighteen-year-old Kate. Rebecca decides to find a permanent home. Via answering machine, Kevin reveals he has married Sophie.

In the present, the noise of a baby music class frightens and upsets Jack. Kate and Toby bicker but make up and take Jack to the beach to learn new sounds. A stinking possum corpse inside Beth's dance studio building threatens her grand opening.

Randall, Beth, and Miguel join newlyweds Kevin and Sophie for dinner at Rebecca and Kate's new house. Kate's coworker, Marc, arrives and introduces himself as her boyfriend; her brothers dislike him. Rebecca cooks an inedible dinner and frets over her children's bickering. Miguel suggests that, like a vintner, she wait out the bad years. Rebecca relates the story of her and Jack's similarly disastrous first dinner in their house, then orders pizza and plays the piano as the family takes Polaroids.

Rebecca's father Dave takes Jack golfing at his country club. Blue-collar Jack feels uncomfortable and drinks heavily. Dave and Jack share competing visions for Rebecca's future. Young Randall idolizes his black teacher, Mr. Lawrence. After Randall expresses interest in Tiger Woods, Jack takes Randall golfing and relates his experience. Randall notes he would not have been allowed at Dave's club. Jack impresses upon Randall the social importance of golf, and Randall plays regularly. Jack invites Lawrence and his wife to dinner, and asks Lawrence to appraise him of Randall's concerns.

Jack, Rebecca, and the young Big Three host Mr. and Mrs. Lawrence for dinner. The interactions between Jack and Lawrence are awkward, but both men are guided by their wives; Rebecca tells Jack that Randall would never choose anyone over him and that Lawrence's mentorship could help Randall, while Lawrence's wife restrains him from overstepping with his enthusiasm for spending time with Randall. Lawrence had planned to gift Randall a copy of Langston Hughes's Weary Blues, but instead gives it to Jack. In the present, Deja accepts Malik's invitation to skip school for a personalized tour of Philadelphia. Deja is scared and confused by her feelings for Malik, and worries about his past.

After Jack's death, Rebecca decides to enter the workforce. She is hired after Randall advocates for her with an interviewer. Randall admits that doing his laundry at home is an excuse to spend time with Rebecca.

On Thanksgiving, 1969, Jack and Nicky ditch their bickering parents to spend the day together. Nicky buys a five-pound shrimp tower and analyzes the song "So Long, Marianne". They agree to spend every Thanksgiving this way, but Nicky is drafted a week later. In the present, Shauna is thriving, but Deja is upset that Shauna wasn't like that for her. Beth reminds Deja that she had "perfect" moments with Shauna. Kevin helps Tess gain the confidence to come out on Instagram. Nicky cries when Randall plays So Long, Marianne and Randall relates Jack's interpretation--Nicky's own, verbatim. Nicky serves the family five pounds of shrimp, a tradition adult Jack Damon preserves in the future.

Reacting to Dave's disapproval, Jack breaks up with Rebecca, saying he can't provide for her. Accepting that Rebecca loves Jack, Janet explains Dave's interference; Janet tells Rebecca that if she chooses Jack, she must make sure their love story is great. Rebecca goes to Jack's auto shop and tells him she loves him, which he reciprocates.

As toddlers, the Big Three sleep in beds for the first time and Randall is scared of monsters; Jack sleeps beside him and asks him to be his typical stable self. Randall goes to sleep, only for Kevin to get up and complain to Jack that he can't sleep. In college, Randall has high-stress nightmares that frighten him. Beth comforts him and suggests he attend a grief group; Randall agrees to go before Rebecca's birthday dinner, but cancels when Kevin informs him of an emergency involving Kate. In the present, Randall offers the intruder money; he takes it and flees.

Toddler Kevin misses a mobile Rebecca donated to Goodwill. Jack tells Kevin that, after losing something he loves, he can find something else to love. As a teenager, Kevin is close with Sophie's loving, supportive, somewhat manic mother Claire. The night of the house fire, a projector malfunction prevents Kevin and Sophie from seeing the end of Good Will Hunting. Leaving it unwatched, they entertain each other with invented endings. After they marry, Kevin asks Claire for her mother's ring, but Claire tells him they have not yet earned it. Rebecca cancels her birthday dinner to help Kate, who calls from the cabin after leaving with Marc.

Toddler Kate wants a "Mommy story." With Rebecca asleep, Jack suggests Kate tell the story, in which she searches for her mother. Teenage Kate struggles to accommodate Marc's moodiness. Rebecca asks to get to know Marc better, which Kate perceives as disapproval of the relationship. Kate decides to skip Rebecca's birthday dinner to write music with Marc at the cabin. Marc quits the record store and expects Kate to quit in solidarity; when she declines, he drives recklessly and kicks Kate out of the car amid insults.

Jack asks the young Big Three to participate in burying a time capsule at the cabin. Randall panics over what to contribute, and Kevin gives him one piece of a family photo jigsaw puzzle to include. Jack sketches a larger house he wants to build on the property. Marc locks teenage Kate out of the cabin in a snowstorm after verbally and emotionally abusing her. Kept away until the next morning by the storm, Rebecca arrives with Kevin and Randall; they quickly find out that Kate broke back into the cabin through a window. Rebecca banishes Marc from the cabin and from Kate's life.

Young Randall obsesses over an A-minus until Jack takes him running. Jack consoles Kate over Stuart ending their relationship, advising that one's first boyfriend is unimportant. Kevin receives two A's in nonacademic electives, nevertheless earning a promised $10 reward from Rebecca. He buys baseball cards, hoping for a '91 John Candelaria, finding one after Rebecca indulges his ritual. In the present, Kevin and Rebecca openly discuss her diagnosis.

Jack and Rebecca take the young Big Three to New York City, where Rebecca has fond childhood memories. Jack gets them lost and feels unable to match Dave's leadership, but Rebecca reassures him. After Rebecca fails to reach the Metropolitan Museum of Art before it closes, Jack takes the family for a hansom cab ride. After Kate and Marc's breakup, Rebecca attends Kevin's acting showcase in the city. Kevin introduces Rebecca to his teacher, Kirby; Rebecca allows Kirby to escort her to the Met, but instead returns alone to her hotel after Kirby ridicules hansom cabs.

In therapy, Randall imagines saving Jack from the fire by demanding he not go back inside for Louie. This brush with mortality leads Rebecca to confess to Jack about knowing William, who becomes part of their lives; Randall attends Carnegie Mellon to stay closer to him, meeting and marrying Beth. With familial support, William's cancer and Rebecca's dementia are caught early. Dr. Leigh challenges Randall's suggestion that he could solve everyone's problems while somehow having the same wife and children, and instructs him to imagine a worst-case scenario. William rejects contact with Randall, who leaves for Howard early and later becomes a professor there.